---
title: "Glossary"
description: "Each HCP term in one line, from Harness Pack and Binding to Sense, land and the four faces, with a link to the page that explains it."
canonical: https://harnesscontextprotocol.io/docs/reference/glossary
---

# Glossary

> Each HCP term in one line, from Harness Pack and Binding to Sense, land and the four faces, with a link to the page that explains it.

Use this table for quick lookup. The normative definitions live in
[§1 Terminology](/docs/specification/terminology), and each row links to the
page that covers the term in full.

| Term | One line | More |
|------|----------|------|
| HCP | Harness Context Protocol: installs a capability into an agent harness as one pack with two loops | [What is HCP](/docs/introduction/what-is-hcp) |
| Harness | The environment an agent runs in: model, tools, memory, policy, runtime | [Concepts](/docs/concepts) |
| Harness Pack | Directory of `surface.json`, `policy.json`, `HARNESS.md` | [Pack](/docs/concepts/pack) |
| Manifest | `surface.json`: identity, adapter, binding, commands, triggers | [Manifest](/docs/packs/manifest) |
| Command | Named operation a pack exposes; wire name `verb_key` | [Command](/docs/concepts/command) |
| `verb_key` | Wire identifier of a command (`plan`, `setup.connect`) | [§3](/docs/specification/manifest) |
| Twin face | A command's CLI form and JSON form produce the same result | [§6.5](/docs/specification/execute) |
| Execute | Inbound loop: an Invoker runs a command | [§6](/docs/specification/execute) |
| Sense | Outbound loop: a pack announces a world change | [§7](/docs/specification/sense) |
| Trigger | Declared Sense event, `stimulusTriggers[].ref` | [Triggers](/docs/concepts/sense#triggers) |
| Policy | Per command or trigger: `operation`, `privacy.land`, `confirm` | [Policy](/docs/concepts/policy) |
| Operation | The effect class of a command, `read` or `write` | [§4.3](/docs/specification/policy) |
| Land | The data domain a command touches: `personal` \| `brain` \| `local` | [§4.4](/docs/specification/policy) |
| Confirm | Gate on writes, satisfied by `args.confirm` or `args.apply` | [§4.5](/docs/specification/policy) |
| Access | The user's or operator's setting for which commands run without asking: mode, rules, approvals | [Access](/docs/concepts/access) |
| Access mode | `manual` \| `auto` \| `run`, how much runs without asking | [Access](/docs/concepts/access#modes) |
| Approval view | The typed card a person sees when a command asks, built from the pack and the call's arguments | [Access](/docs/concepts/access#what-the-card-shows) |
| Command title | The pack's words for a step, `live` while it runs and `done` after | [Command](/docs/concepts/command#titles) |
| Binding | How a command gets credentials at exec time: mode and hub, never a secret | [Binding](/docs/concepts/binding) |
| Mode | `public` \| `user` \| `local` \| `mothership` \| `mock` | [§8.2](/docs/specification/binding) |
| Hub | Component kind that mints: `keyring`, `local-credential`, `public`, `none` | [§8.3](/docs/specification/binding) |
| Family | Group of packs sharing one consent | [§8.3](/docs/specification/binding) |
| Mint | The runtime gets a credential from the hub for one exec | [§8.4](/docs/specification/binding) |
| Connect | Lifecycle step that establishes Binding; capability `pack.connect` | [§8.5](/docs/specification/binding) |
| Principal | The acting identity: human, service, agent or mothership | [Principal](/docs/concepts/binding#principal) |
| Mothership | Operator or fleet identity; the Binding mode for control-plane packs | [§8.2](/docs/specification/binding) |
| Tenant | Organisational scope from the session, never from args | [§9.2](/docs/specification/authorization) |
| Project | Sub-scope required for land `brain` | [§9.2](/docs/specification/authorization) |
| Capability | One of five grant axes | [§9.4](/docs/specification/authorization) |
| Grant | `{ capability, pack_id?, verb_keys? }` held by a Principal | [Authorization](/docs/concepts/access#authorization) |
| Invoker | Who calls Execute: agent tool, API, UI, human CLI | [Invoker](/docs/runtimes/execution#invoker) |
| Adapter | How a command runs: `wrap`, `composite`, `openapi`, `sense_only` | [Adapter](/docs/concepts/adapter) |
| Wrap | Adapter that spawns `wrap.bin` with rendered argv | [Wrap a CLI](/docs/packs/wrap-a-cli) |
| Composite | In-process adapter | [Adapter](/docs/concepts/adapter) |
| Pass-through | Bootstrap-only whole-CLI wrap with allowed subcommands | [§3.3](/docs/specification/manifest) |
| Plane | `runtime` (user work) or `control` (operator lifecycle) | [§2.5](/docs/specification/pack-model) |
| Runtime | Loads, authorises, binds, executes, routes Sense | [Build runtimes](/docs/runtimes) |
| Reference runtime | `createReferenceLocalRuntime` in the SDK | [SDK](/docs/reference/sdk#runtime-drivers) |
| Host | An agent product that adopts HCP | [Adopt in hosts](/docs/hosts) |
| Projection | A pack's view on a surface: CLI, host tool, Skill, MCP export | [§12](/docs/specification/projections) |
| Four faces | Wire, CLI, host tool and Skill must name a command consistently | [§12.4](/docs/specification/projections) |
| Skill | `HARNESS.md`, the teaching document for humans and agents | [Skill](/docs/concepts/skill) |
| Lead | Text between the Skill title and first `##`; the stable-context excerpt | [§5.3](/docs/specification/skill) |
| Sandbox | Default exec posture: bin allow-list, cwd jail, no ambient credentials | [§10](/docs/specification/sandbox) |
| Native-local | Explicit opt-out of the jail on a trusted machine | [§10.3](/docs/specification/sandbox) |
| Availability | `installed` / `activated` / `connected` / `executable` | [§11.2](/docs/specification/lifecycle) |
| Store | `$HCP_HOME`, which holds packs, skills and state | [CLI](/docs/reference/cli#store) |
| `hcpx` | The reference CLI's binary, also installed as `hcp` | [Quickstart](/docs/quickstart#one-binary-two-names) |
| Eval case | One expectation about a command in `hcp.eval.json`, run through the runtime by `hcpx eval` | [Check and evaluate](/docs/packs/check#eval-cases) |
| Bootstrap pack | `hcp-cli`, which describes the runtime's own lifecycle | [§11.4](/docs/specification/lifecycle) |
| Gold pack | A reference pack that ships with the SDK (`transit`, `ledger`, `echo`) | [Examples](/docs/packs/examples) |
| Sink | Where Sense records land: `inbox` or `silent` | [Sense delivery](/docs/concepts/sense#sense-delivery) |
| Conformance vector | Executable test tied to a spec section | [§14](/docs/specification/conformance) |
| RFC | Change proposal to the protocol | [RFC process](/docs/community/governance#rfc-process) |
| Agent Skills | External standard for teaching documents; `HARNESS.md` is compatible | [Landscape](/docs/introduction/landscape) |
| MCP | Model Context Protocol, a transport HCP can export to | [Landscape](/docs/introduction/landscape) |
| Connector | Not an HCP type; a vendor SDK inside a product runtime | [Landscape](/docs/introduction/landscape) |

## Sitemap

- [Documentation](https://harnesscontextprotocol.io/docs)
- [Packs](https://harnesscontextprotocol.io/packs)
- [Glossary](https://harnesscontextprotocol.io/docs/reference/glossary)
- [llms.txt](https://harnesscontextprotocol.io/llms.txt)
- [llms-full.txt](https://harnesscontextprotocol.io/llms-full.txt)
- [OpenAPI](https://harnesscontextprotocol.io/openapi.json)
- [MCP](https://harnesscontextprotocol.io/mcp)